US6285566B1 - RCC power supply with remote disabling of oscillation frequency control - Google Patents

RCC power supply with remote disabling of oscillation frequency control Download PDF

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Publication number
US6285566B1
US6285566B1 US09/234,958 US23495899A US6285566B1 US 6285566 B1 US6285566 B1 US 6285566B1 US 23495899 A US23495899 A US 23495899A US 6285566 B1 US6285566 B1 US 6285566B1
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control
transistor
switching
oscillation
self
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Expired - Fee Related
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US09/234,958
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Koji Nakahira
Ryuji Okamura
Ryota Tani
Akio Nishida
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Murata Manufacturing Co Ltd
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Murata Manufacturing Co Ltd
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Assigned to MURATA MANUFACTURING CO., LTD. reassignment MURATA MANUFACTURING CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: NAKAHIRA, KOJI, NISHIDA, AKIO, OKAMURA, RYUJI, TANI, RYOTA
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of DC power input into DC power output
    • H02M3/22—Conversion of DC power input into DC power output with intermediate conversion into AC
    • H02M3/24—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters
    • H02M3/28—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC
    • H02M3/325—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/338—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only in a self-oscillating arrangement
    • H02M3/3385—Conversion of DC power input into DC power output with intermediate conversion into AC by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate AC using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only in a self-oscillating arrangement with automatic control of output voltage or current

Definitions

  • the present invention relates to a self-oscillation switching power supply apparatus.
  • FIG. 9 is a circuit diagram of a ringing choke converter (hereinafter referred to as an RCC) according to a conventional technique.
  • a switching transistor Q 1 is connected in series to a primary winding N 1 of a transformer T.
  • a control circuit including a phototransistor PT serving as a photosensing element of a photocoupler is connected to a feedback winding N B of the transformer.
  • a control transistor Q 2 is connected between the gate and the source of the switching transistor Q 1 .
  • a rectifying and smoothing circuit including a rectifying diode D 3 and a smoothing capacitor C 5 is disposed between two terminals of a secondary winding N 2 of the transformer T.
  • the output of this rectifying and smoothing circuit is connected to a voltage detecting circuit including a resistance voltage divider consisting of resistors R 9 and R 10 , a shunt regulator SR, a light emitting diode PD of the photocoupler PC, and a resistor R 8 .
  • the circuit shown in FIG. 9 operates as follows.
  • a voltage is applied to the gate of the switching transistor Q 1 via the starting resistor R 1 and the switching transistor Q 1 turns on.
  • an input power supply voltage is applied across the primary winding N 1 of the transformer T and a voltage with the same polarity as that of the primary winding N 1 is generated across the feedback winding N B .
  • This voltage signal is applied as a positive feedback signal to the gate of the switching transistor Q 1 via a capacitor C 2 and a resistor R 2 .
  • the voltage induced across the feedback winding N B causes a charging current to flow into a capacitor C 3 via a diode D 1 , resistors R 3 and R 5 , and the phototransistor PT of the photocoupler. If the voltage across the capacitor C 3 exceeds the forward base-emitter voltage of the control transistor Q 2 , the control transistor Q 2 turns on. As a result, the gate-source voltage of the switching transistor Q 1 becomes nearly 0 and thus the switching transistor Q 1 is forced to turn off. As a result, a voltage is generated across the secondary winding of the transformer. This causes the rectifying diode D 3 to have a voltage applied in the forward direction.
  • the control transistor Q 2 turns off and the energy stored in the transformer T is released from the secondary winding. If the current passing through the rectifying diode D 3 becomes 0, a kick voltage is induced across the feedback winding N B whereby the switching transistor Q 1 again turns on. After that, the above process is repeated.
  • the output voltage across the load is detected by means of a resistance divider comprising resistors R 9 and R 10 and the detected voltage is applied as a control voltage to the shunt regulator SR.
  • the shunt regulator SR changes the current passing through the light emitting diode PD of the photocoupler.
  • a corresponding change occurs in the amount of light received by the phototransistor PT serving as the photosensing element of the photocoupler, and thus the impedance of the phototransistor PT changes. This causes a corresponding change in the charging time constant associated with the capacitor C 3 .
  • a reduction in the output voltage results in an increase in the period of time from an off-to-on transition of the switching transistor Q 1 to the following on-to-off transition forcedly brought about by the control transistor Q 2 , that is, an increase in the on-time of the switching transistor Q 1 , which results in an increase in the output voltage.
  • the output voltage is controlled at a constant value.
  • the oscillation frequency f of the switching transistor Q 1 in the conventional self-oscillation switching power supply apparatus such as that shown in FIG. 9 varies in approximately inverse proportion to the input or output power as shown in FIG. 10 in which the oscillation frequency f is plotted as a function of the output power Po.
  • the switching loss which occurs during each switching operation decreases with the reduction in the load.
  • the oscillation frequency f increases, as shown in FIG. 10, with the reduction in the output power Po and thus with the reduction in the load, the frequency of occurrence of switching loss per unit time increases with the increase in the oscillation frequency f. Therefore, the reduction in the switching loss which occurs when the load decreases is very small. This means that the efficiency of the power supply apparatus decreases with the reduction in the load.
  • the switching loss under low load condition can be reduced by designing the circuit parameters such that the oscillation frequency for the operation under the rated-load condition becomes low enough.
  • the oscillation frequency f under the low load condition is generally determined by factors associated with components such as the magnetic flux density of the transformer and other factors such as ripples and noise. If the oscillation frequency is set to a too low value, problems such as saturation of the transformer occur.
  • the present invention is directed to self-oscillation switching power supply apparatus that satisfied this need.
  • the self-oscillation switching power supply apparatus is a ringing choke converter type and comprises: a transformer T including a primary winding N 1 , a secondary winding N 2 , and a feedback winding N B ; a switching transistor Q 1 which oscillates in a self-oscillating fashion in response to a feedback signal from the feedback winding N B thereby turning on and off the current flowing through the primary winding; and a rectifying and smoothing circuit connected to said secondary winding.
  • the self-oscillation switching power supply apparatus further comprises: an oscillation frequency control circuit including a control transistor Q 3 for controlling a control signal input to the switching transistor Q 1 thereby controlling the control transistor Q 3 so as to extend the off-time in the self-oscillation period of the switching transistor Q 1 ; and an oscillation frequency control disabling circuit for disabling the control of the control transistor Q 3 in accordance with a remote signal.
  • an oscillation frequency control circuit including a control transistor Q 3 for controlling a control signal input to the switching transistor Q 1 thereby controlling the control transistor Q 3 so as to extend the off-time in the self-oscillation period of the switching transistor Q 1 ; and an oscillation frequency control disabling circuit for disabling the control of the control transistor Q 3 in accordance with a remote signal.
  • the oscillation frequency control circuit controls the control transistor Q 3 thereby controlling the switching transistor Q 1 so as to extend the off-time in the self-oscillation period of the switching transistor Q 1 .
  • the switching frequency of the switching transistor Q 1 becomes lower than would be if there were not provided the oscillation frequency control circuit. If a remote signal is received from the outside, the control of the control transistor Q 3 is disabled and thus the self-oscillation switching power supply apparatus operates as a self-oscillation switching power supply apparatus of the normal RCC type. This allows the self-oscillation switching power supply apparatus to generate a power supply voltage for a wide range of loads.
  • the self-oscillation switching power supply apparatus may includes a starting circuit for supplying a starting signal to the control signal input of the switching transistor Q 1 ; and a rectifying and smoothing circuit for rectifying and smoothing a voltage generated across the feedback winding N B , the rectifying and smoothing circuit being disposed between the control signal input of the switching transistor Q 1 and the feedback winding N B .
  • a current supplied from both the starting circuit and the rectifying and smoothing circuit serves as a control signal for controlling the switching transistor.
  • the off-time of the switching transistor varies. Therefore, the rectifying and smoothing circuit causes an increase in the oscillation frequency.
  • the switching frequency of the switching transistor Q 1 is reduced by the above-described oscillation frequency control circuit.
  • the power loss in the waiting state is reduced.
  • the switching frequency is reduced to a too low value in the audio-frequency range, the switching operation can cause audible noise.
  • This problem can be avoided by providing the above-described rectifying and smoothing circuit. If the starting current from the starting circuit is increased, the off-time of the switching transistor becomes shorter and thus the oscillation frequency becomes higher. However, the increase in the current from the starting circuit results in an increase in the power loss due to the starting circuit because the current from the starting circuit always flows regardless of whether the apparatus is in the waiting state or not. This problem is avoided by providing the above-described rectifying and smoothing circuit. That is, it is possible to independently set the off-time of the switching transistor and the starting current flowing through the starting circuit.
  • FIG. 1 is a circuit diagram of a self-oscillation switching power supply apparatus according to a first embodiment.
  • FIG. 2 is a graph illustrating the output power of the self-oscillation switching power supply apparatus according to the first embodiment as a function of frequency.
  • FIG. 3A is a graph illustrating waveforms at various points of the self-oscillation switching power supply apparatus according to the first embodiment
  • FIG. 3B is an enlarged graph thereof.
  • FIG. 4A is a graph illustrating waveforms at various points of the self-oscillation switching power supply apparatus according to the first embodiment, and FIG. 4B is an enlarged graph thereof.
  • FIG. 5 is a circuit diagram of a self-oscillation switching power supply apparatus according to a second embodiment.
  • FIG. 6 is a circuit diagram of a self-oscillation switching power supply apparatus according to a third embodiment.
  • FIG. 7 is a circuit diagram of a self-oscillation switching power supply apparatus according to a fourth embodiment.
  • FIG. 8 is a circuit diagram of a self-oscillation switching power supply apparatus according to a fifth embodiment.
  • FIG. 9 is a circuit diagram of a self-oscillation switching power supply apparatus according to a conventional technique.
  • FIG. 10 is a graph illustrating the output power of the self-oscillation switching power supply apparatus according to the conventional technique as a function of frequency.
  • FIG. 1 is a circuit diagram of the self-oscillation switching power supply apparatus.
  • a MOS-FET serving as a switching transistor Q 1 is connected to a primary winding N 1 of a transformer T and there is provided a feedback circuit from a feedback winding N B of the transformer T to the switching transistor Q 1 .
  • a rectifying and smoothing circuit including a rectifying diode D 3 and a smoothing capacitor C 5 is connected to a secondary winding N 2 of the transformer T.
  • the output of the rectifying and smoothing circuit is connected to a voltage detecting circuit including a resistance voltage divider consisting of resistors R 9 and R 10 , a shunt regulator SR, a light emitting element PD 1 of a first photocoupler, and a resistor R 8 .
  • FIG. 1 when a remote signal REM with a high-level value is applied from the outside to a light emitting element PD 2 of a second photocoupler, the light emitting element PD 2 emits light and thus a phototransistor PT 2 serving as a photosensing element of the second photocoupler turns on.
  • a control transistor Q 3 according to the present invention is connected, via a diode D 41 , between the gate and the source of the switching transistor Q 1 .
  • the above-described remote signal REM is at a high level.
  • the control transistor Q 3 is maintained in an off-state and the switching power apparatus operates as a self-oscillation switching power supply of the conventional RCC type.
  • the phototransistor PT 2 of the second photocoupler turns off and the control transistor Q 3 turns on and off in accordance with the circuit connected to the base of the control transistor Q 3 .
  • reference numeral 1 denotes a part corresponding to an oscillation frequency control circuit according to the invention and reference numeral 2 denotes a part corresponding to an oscillation frequency control disabling circuit according to the invention.
  • FIGS. 3A and 4A illustrate voltage waveforms at various points in FIG. 1 .
  • V NB denotes the voltage across the feedback winding N B
  • Vc 41 denotes the voltage across a capacitor C 41
  • V BE denotes the base-emitter voltage of the control transistor Q 3
  • V G denotes the gate-source voltage of the switching transistor Q 1
  • Vd denotes the drain voltage of the switching transistor Q 1
  • Id denotes the drain current of the switching transistor Q 1
  • I D3 denotes the waveform of the current flowing through a rectifying diode D 3 connected to the secondary winding.
  • FIGS. 3B and 4B are expanded by a factor of 10 with respect to those of FIGS. 3A and 4A, respectively.
  • the operations at times denoted by (a)-(d) in FIGS. 3 and 4 are described below.
  • the voltage is set such that V NB ⁇ V F +V Z +(1+R 43 /R 44 )Vbe where V F is the forward voltage drop of the diode D 43 , V Z is the Zener voltage of the Zener diode D 44 , and Vbe is the base-emitter voltage required to turn on the transistor Q 4 .
  • V F is the forward voltage drop of the diode D 43
  • V Z is the Zener voltage of the Zener diode D 44
  • Vbe is the base-emitter voltage required to turn on the transistor Q 4 .
  • the transistor Q 4 turns on before the control transistor Q 3 turns on.
  • the base voltage of transistor Q 3 becomes zero and transistor Q 3 remains in the off-state.
  • a voltage indicated by an arrow in FIG. 3B denotes the Zener voltage of the Zener diode D 44 (more exactly, the voltage is equal to the sum of the Zener voltage of the Zener diode D 33 and the forward voltage of the diode D 44 ).
  • the switching transistor Q 1 does not turn on immediately after the turning-off of the control transistor Q 3 , but the switching transistor Q 1 turns on when the gate voltage of the switching transistor Q 1 reaches the threshold voltage after increasing at a speed with a time constant determined by the resistances R 1 and R 12 and the input capacitance between the gate and the source of transistor Q 1 .
  • the state returns to that described in (a). After that, the processes (a)-(d) are repeated.
  • the off-time of the self-oscillation period of the switching transistor Q 1 is extended and thus the oscillation frequency f becomes low.
  • the phototransistor PT 2 turns on and the control transistor Q 3 is maintained in the off-state as described earlier.
  • the oscillation frequency control circuit 1 which extends the off-time in the self-oscillation period of the switching transistor Q 1 , is disabled and thus the switching power supply apparatus operates as a normal RCC type self-oscillation switching power supply apparatus.
  • the switching transistor Q 1 is turned on by a kick voltage which is generated when the rectifying diode D 3 connected to the secondary winding of the transformer T cuts off and the current becomes 0. That is, the switching transistor Q 1 turns on at a time denoted by (c) in FIG. 3 and thus oscillation occurs at a high frequency.
  • FIG. 2 illustrates the relationship between the output power of the above-described power supply apparatus and the oscillation frequency.
  • the oscillation frequency In the waiting state, as can be seen from FIG. 2, the oscillation frequency is forced to a low value so that the switching loss is maintained at a low level.
  • the oscillation frequency decreases with the increase in the load so that the power supply apparatus can have a high current capacity when the load becomes large.
  • FIG. 5 is a circuit diagram of a self-oscillation switching power supply apparatus according to a second embodiment.
  • This circuit is different from that shown in FIG. 1 in terms of the location of the phototransistor PT 2 serving as the photosensing element, for receiving the remote signal, of the second photocoupler. That is, in this second embodiment, PT 2 is connected in series to the resistor R 41 .
  • the resistance division ratio associated with the resistors R 41 and R 42 and the phototransistor PT 2 changes in an opposite fashion to FIG. 1 . That is, when PT 2 is in an on-state, the control transistor Q 3 periodically turns on and off while the control transistor Q 3 is maintained in an off-state when PT 2 is in an off-state.
  • FIG. 6 is a circuit diagram of a self-oscillation switching power supply apparatus according to a third embodiment.
  • the switching transistor Q 1 in the circuit shown in FIG. 1 is replaced with a bipolar transistor.
  • an additional diode D 50 is provided in the feedback path from the feedback winding N B to the base of the switching transistor Q 1 .
  • a current signal is positively fed back from the feedback winding N B to the base of the switching transistor Q 1 . Except for this point, the circuit operates in the same manner as the first embodiment.
  • FIG. 7 is a circuit diagram of a self-oscillation switching power supply apparatus according to a fourth embodiment.
  • the switching transistor Q 1 in the circuit shown in FIG. 5 is replaced with a bipolar transistor.
  • the general operation of this circuit is similar to the circuit according to the second embodiment.
  • FIG. 8 is a circuit diagram of a self-oscillation switching power supply apparatus according to a fifth embodiment.
  • the circuit according to this fifth embodiment is equivalent to a circuit obtained by adding a rectifying and smoothing circuit 4 to the circuit shown in FIG. 1 .
  • reference numeral 4 denotes a rectifying and smoothing circuit including a diode D 45 for rectifying a voltage generated across the feedback winding N B , a capacitor C 42 for smoothing the rectified voltage, and a resistor R 45 through which the smoothed voltage is applied to the gate of the switching transistor Q 1 .
  • Reference numeral 3 denotes a starting circuit including a starting resistor R 1 through which a starting current is supplied to the gate of the switching transistor Q 1 .
  • the other parts in FIG. 8 are similar to those in FIG. 1 .
  • the capacitor C 42 is charged by a voltage generated across the feedback winding N B during the on-period of the switching transistor Q 1 .
  • the charge stored in the capacitor C 42 flows as a current into the resistor R 12 via the resistor R 45 and also as a charging current to the gate-source capacitance of the switching transistor Q 1 .
  • a part of the current flowing into the resistor R 12 is also supplied via the starting resistor R 1 and a part of the charging current into the gate-source capacitance of the switching transistor Q 1 is also supplied via the starting resistor R 1 . That is, the current flowing into the gate-source capacitance of the switching transistor Q 1 is given as the sum of the current supplied from the rectifying and smoothing circuit 4 and the current supplied from the starting circuit 3 .
  • the oscillation frequency can be increased by the rectifying and smoothing circuit 4 .
  • the power loss can be reduced by reducing the switching frequency of the switching transistor Q 1 by means of the oscillation frequency control circuit 1 . Furthermore, the oscillation frequency control circuit 1 prevents the switching frequency from decreasing down to a too low value in the audio-frequency range. Because it is not required to increase the staring current from the starting circuit to increase the oscillation frequency, the current from the starting circuit can be set to a minimum required value so that the power loss associated with the starting circuit is minimized.
  • the rectifying and smoothing circuit 4 may also be added to the circuits shown in FIGS. 5, 6 , and 7 so as to achieve similar effects.

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  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)
US09/234,958 1998-02-09 1999-01-21 RCC power supply with remote disabling of oscillation frequency control Expired - Fee Related US6285566B1 (en)

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JP10027037A JPH11235036A (ja) 1998-02-09 1998-02-09 自励発振型スイッチング電源装置
JP10-027037 1998-02-09

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Cited By (15)

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US6529392B2 (en) * 2000-09-06 2003-03-04 Murata Manufacturing Co., Ltd. Switching power supply unit
US6608768B2 (en) * 2001-08-07 2003-08-19 Salcomp Oy Use of a rectified image voltage for controlling the switch on the primary side of a switched-mode power supply
US20040252526A1 (en) * 2003-06-16 2004-12-16 Smk Corporation Self-excited switching power supply circuit
US20050024895A1 (en) * 2003-07-29 2005-02-03 Mabanta Samuel P. Switching-bursting method and apparatus for reducing standby power and improving load regulation in a DC-DC converter
US20060133117A1 (en) * 2003-07-15 2006-06-22 Genannt Berghegger Ralf S Simple switched-mode power supply with current and voltage limitation
US20080007976A1 (en) * 2006-06-16 2008-01-10 Rohm Co., Ltd. Power supply device and electric appliance provided therewith
US20090303752A1 (en) * 2006-06-30 2009-12-10 Panasonic Electric Works Co., Ltd. Switching Power Supply
US20100149840A1 (en) * 2008-12-15 2010-06-17 Canon Kabushiki Kaisha Power supply apparatus and image forming apparatus
US20100232186A1 (en) * 2009-03-13 2010-09-16 Canon Kabushiki Kaisha Switching power supply device
US20120140530A1 (en) * 2010-12-06 2012-06-07 Canon Kabushiki Kaisha Switching power supply apparatus and image forming apparatus
US20120280670A1 (en) * 1998-02-27 2012-11-08 Power Integrations, Inc. Off-line converter with digital control
US20140043869A1 (en) * 2012-08-10 2014-02-13 Canon Kabushiki Kaisha Power supply apparatus and image forming apparatus
US8654547B2 (en) 2005-08-26 2014-02-18 Power Integrations, Inc. Method and apparatus for digital control of a switching regulator
US20140185332A1 (en) * 2012-01-11 2014-07-03 Panasonic Corporation Switching power supply circuit
US12294307B2 (en) * 2021-08-27 2025-05-06 Na Vitas Semiconductor Limited System and methods for reducing auxiliary transformer winding turns

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JP3470693B2 (ja) 2000-10-25 2003-11-25 株式会社村田製作所 自励発振型スイッチング電源装置
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JP4668473B2 (ja) * 2001-07-26 2011-04-13 ニチコン株式会社 スイッチング電源
KR100903609B1 (ko) * 2002-09-23 2009-06-18 삼성에스디아이 주식회사 링깅 초크 컨버터 방식의 전원 제어 회로
JP4993510B2 (ja) * 2008-09-05 2012-08-08 株式会社ナナオ 省電力電源装置

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Cited By (28)

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Publication number Priority date Publication date Assignee Title
US8710817B2 (en) * 1998-02-27 2014-04-29 Power Integrations, Inc. Off-line converter with digital control
US20120280670A1 (en) * 1998-02-27 2012-11-08 Power Integrations, Inc. Off-line converter with digital control
US6529392B2 (en) * 2000-09-06 2003-03-04 Murata Manufacturing Co., Ltd. Switching power supply unit
US6608768B2 (en) * 2001-08-07 2003-08-19 Salcomp Oy Use of a rectified image voltage for controlling the switch on the primary side of a switched-mode power supply
US20040252526A1 (en) * 2003-06-16 2004-12-16 Smk Corporation Self-excited switching power supply circuit
US7012816B2 (en) * 2003-06-16 2006-03-14 Smk Corporation Self-excited switching power supply circuit
US7295449B2 (en) * 2003-07-15 2007-11-13 Friwo Mobile Power Gmbh Simple switched-mode power supply with current and voltage limitation
US20060133117A1 (en) * 2003-07-15 2006-06-22 Genannt Berghegger Ralf S Simple switched-mode power supply with current and voltage limitation
US20050024895A1 (en) * 2003-07-29 2005-02-03 Mabanta Samuel P. Switching-bursting method and apparatus for reducing standby power and improving load regulation in a DC-DC converter
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US10224820B2 (en) 2005-08-26 2019-03-05 Power Integrations, Inc. Method and apparatus for digital control of a switching regulator
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Publication number Publication date
JPH11235036A (ja) 1999-08-27
EP0935332A2 (de) 1999-08-11
EP0935332A3 (de) 2000-02-23

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